Babelchord: a social tower of DHT-based overlay networks

Abstract

Chord is a protocol to distribute and retrieve information at large scale. It builds a large but rigid overlay network without taking into account the social nature and the underlying topology of large platforms, made of the interconnection of many independent smaller networks. Thus, new approaches are required to build overlay networks. In this paper, we propose Babelchord, a more flexible and social overlay interconnecting different Chord networks, which are floors of a social tower. Peers can belong to several floors, allowing this interconnection. By connecting smaller structured overlay networks in an unstructured way, it provides a costeffective alternative to hierarchical structured P2P systems requiring costly merging. Routing of lookup messages is performed as in Chord within one floor, but a peer belonging to several floors forwards the request to the different floors it belongs to. These co-located peers act as a sort of neural synapse. Results from simulations show that Babelchord scales up logarithmically with the number of Babelchord peers. Moreover a small number of synapses is enough to ensure a high exhaustiveness level.

Synapse: A Scalable Protocol for Interconnecting Heterogeneous Overlay Networks

“…In our previous preliminary work [13], we introduced BabelChord, a protocol for inter-connecting Chord overlay networks using co-located nodes that are part of multiple Chord "floors". These nodes connect, in an unstructured fashion, several Chord overlays together.…”

Backward-Compatible Cooperation of Heterogeneous P2P Systems

“…In [5][6][7][8], the authors deal with inter-overlay routing by using co-located nodes, i.e. nodes belonging to multiple overlays at the same time, as gateways forwarding messages between overlays.…”

“…The co-located nodes also perform the transcoding of queries between overlays. In [5], the original queries from peers in one DHT are sent to the trackers that, in turn, forward them to co-located nodes, in order to reach other DHT s. In [6,7] the messages from one DHT are forwarded to others only if they randomly touch the co-located nodes while in [8], the co-located nodes have some auto discovery mechanisms to detect each other, thus the original messages can be sent directly between them.…”

“…While the solutions in [5][6][7] are only for DHT s, i.e. structured overlays, the solution in [8] is for both structured and unstructured overlays.…”

“…structured overlays, the solution in [8] is for both structured and unstructured overlays. The solution in [6,7] requires the modification of all peers in overlays, i.e. peers which are unaware of new protocols cannot operate, which is not practical in reality.…”